/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.tomcat.util.http.fileupload.util;

import org.apache.tomcat.util.http.fileupload.IOUtils;
import org.apache.tomcat.util.http.fileupload.InvalidFileNameException;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * Utility class for working with streams.
 */
public final class Streams {

	/**
	 * Default buffer size for use in
	 * {@link #copy(InputStream, OutputStream, boolean)}.
	 */
	private static final int DEFAULT_BUFFER_SIZE = 8192;

	/**
	 * Private constructor, to prevent instantiation.
	 * This class has only static methods.
	 */
	private Streams() {
		// Does nothing
	}

	/**
	 * Copies the contents of the given {@link InputStream}
	 * to the given {@link OutputStream}. Shortcut for
	 * <pre>
	 *   copy(pInputStream, pOutputStream, new byte[8192]);
	 * </pre>
	 *
	 * @param inputStream       The input stream, which is being read.
	 *                          It is guaranteed, that {@link InputStream#close()} is called
	 *                          on the stream.
	 * @param outputStream      The output stream, to which data should
	 *                          be written. May be null, in which case the input streams
	 *                          contents are simply discarded.
	 * @param closeOutputStream True guarantees, that {@link OutputStream#close()}
	 *                          is called on the stream. False indicates, that only
	 *                          {@link OutputStream#flush()} should be called finally.
	 * @return Number of bytes, which have been copied.
	 * @throws IOException An I/O error occurred.
	 */
	public static long copy(InputStream inputStream, OutputStream outputStream, boolean closeOutputStream)
			throws IOException {
		return copy(inputStream, outputStream, closeOutputStream, new byte[DEFAULT_BUFFER_SIZE]);
	}

	/**
	 * Copies the contents of the given {@link InputStream}
	 * to the given {@link OutputStream}.
	 *
	 * @param inputStream       The input stream, which is being read.
	 *                          It is guaranteed, that {@link InputStream#close()} is called
	 *                          on the stream.
	 * @param outputStream      The output stream, to which data should
	 *                          be written. May be null, in which case the input streams
	 *                          contents are simply discarded.
	 * @param closeOutputStream True guarantees, that {@link OutputStream#close()}
	 *                          is called on the stream. False indicates, that only
	 *                          {@link OutputStream#flush()} should be called finally.
	 * @param buffer            Temporary buffer, which is to be used for
	 *                          copying data.
	 * @return Number of bytes, which have been copied.
	 * @throws IOException An I/O error occurred.
	 */
	public static long copy(InputStream inputStream,
	                        OutputStream outputStream, boolean closeOutputStream,
	                        byte[] buffer)
			throws IOException {
		OutputStream out = outputStream;
		InputStream in = inputStream;
		try {
			long total = 0;
			for (; ; ) {
				int res = in.read(buffer);
				if (res == -1) {
					break;
				}
				if (res > 0) {
					total += res;
					if (out != null) {
						out.write(buffer, 0, res);
					}
				}
			}
			if (out != null) {
				if (closeOutputStream) {
					out.close();
				} else {
					out.flush();
				}
				out = null;
			}
			in.close();
			in = null;
			return total;
		} finally {
			IOUtils.closeQuietly(in);
			if (closeOutputStream) {
				IOUtils.closeQuietly(out);
			}
		}
	}

	/**
	 * This convenience method allows to read a
	 * {@link org.apache.tomcat.util.http.fileupload.FileItemStream}'s
	 * content into a string. The platform's default character encoding
	 * is used for converting bytes into characters.
	 *
	 * @param inputStream The input stream to read.
	 * @return The streams contents, as a string.
	 * @throws IOException An I/O error occurred.
	 * @see #asString(InputStream, String)
	 */
	public static String asString(InputStream inputStream) throws IOException {
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		copy(inputStream, baos, true);
		return baos.toString();
	}

	/**
	 * This convenience method allows to read a
	 * {@link org.apache.tomcat.util.http.fileupload.FileItemStream}'s
	 * content into a string, using the given character encoding.
	 *
	 * @param inputStream The input stream to read.
	 * @param encoding    The character encoding, typically "UTF-8".
	 * @return The streams contents, as a string.
	 * @throws IOException An I/O error occurred.
	 * @see #asString(InputStream)
	 */
	public static String asString(InputStream inputStream, String encoding) throws IOException {
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		copy(inputStream, baos, true);
		return baos.toString(encoding);
	}

	/**
	 * Checks, whether the given file name is valid in the sense,
	 * that it doesn't contain any NUL characters. If the file name
	 * is valid, it will be returned without any modifications. Otherwise,
	 * an {@link InvalidFileNameException} is raised.
	 *
	 * @param fileName The file name to check
	 * @return Unmodified file name, if valid.
	 * @throws InvalidFileNameException The file name was found to be invalid.
	 */
	public static String checkFileName(String fileName) {
		if (fileName != null && fileName.indexOf('\u0000') != -1) {
			// pFileName.replace("\u0000", "\\0")
			final StringBuilder sb = new StringBuilder();
			for (int i = 0; i < fileName.length(); i++) {
				char c = fileName.charAt(i);
				switch (c) {
					case 0:
						sb.append("\\0");
						break;
					default:
						sb.append(c);
						break;
				}
			}
			throw new InvalidFileNameException(fileName,
					"Invalid file name: " + sb);
		}
		return fileName;
	}

}
